Arne-Jörn Lemke

MRI after magnetic drug targeting in patients with advanced solid malignant tumors

The purpose of this study was to evaluate the ability of MRI to detect magnetic particle uptake into advanced solid malignant tumors and to document the extension of these tumors, carried out in the context of magnetic drug targeting. In a prospective phase I trial, 11 patients were examined with MRI before and after magnetic drug targeting. The sequence protocol included T1-WI and T2-WI in several planes, followed by quantitative and qualitative evaluation of the signal intensities and tumor extensions. In nine patients, a signal decrease was observed in the early follow-up (2–7 days after therapy) on the T2-weighted images; two patients did not show a signal change. The signal changes in T1-WI were less distinct. In late follow-up (4–6 weeks after therapy), signal within nine tumors reached their initially normal level on both T1-WI and T2-WI; two tumors showed a slight signal decrease on T2-WI and a slight signal increase on T1-WI. Within the surveillance period, tumor remission in 3 out of 11 patients was observed, and in 5 patients tumor growth had stopped. The remaining three patients showed significant tumor growth. There was no statistically significant correlation between signal change and response. MRI is a suitable method to detect magnetite particles, deposited at the tumor site via magnetic drug targeting. MRI is therefore eligible to control the success of MDT and to assess the tumor size after the end of therapy.

Contrast-enhanced power Doppler sonography: Improved detection of characteristic flow patterns in focal liver lesions

The aim of this study was to evaluate whether intravenous injection of an ultrasound contrast agent aids in the visualization of focal liver lesions on power Doppler images.

Retinoblastoma—MR appearance using a surface coil in comparison with histopathological results

PurposeThe purpose of this work was to evaluate the characteristic appearance of untreated retinoblastoma on a large sample in comparison to the histological findings after therapeutical enucleation.Materials and methodsIn a prospective clinical trial 46 children with retinoblastoma in 63 affected untreated eyes were examined under general anesthesia on MRI using a 1.5-T system. The examinations were performed with a special surface coil applying an examination protocol including fast T2- and T1-weighted spin echo sequences and additional fast T1-WI after intravenous injection of Gd-DTPA in different planes. The imaging results were compared to the histopathological findings in 29 patients with 30 affected eyes.ResultsComparing MRI findings and histopathological results, optic nerve infiltration was detected with a sensitivity of 53.8% and a specificity of 82.3% on MRI, infiltration of the choroid with a sensitivity of 75.0% and a specificity of 100.0%, and the degree of tumor calcification with a sensitivity of 91.7% and a specificity of 88.9%. In this study the characteristic MR appearance of untreated retinoblastoma was evaluated.ConclusionMRI was helpful in relevant aspects of pretherapeutical retinoblastoma staging, deficits remain regarding optic nerve infiltration.

Intraocular metastases: differential diagnosis from uveal melanomas with high-resolution MRI using a surface coil

Magnetic resonance imaging with dedicated surface coils plays a pivotal role in differential diagnosis and staging of intraocular tumors. The purpose of this study was to establish MRI criteria for the differential diagnosis of uveal melanomas and intraocular metastases. In a prospective study 44 eyes in 36 patients with intraocular metastases and 200 patients with uveal melanomas were investigated with MRI using a 1.5-T scanner and a 5-cm surface coil. Both quantitative and qualitative evaluation of the resulting images was performed. The MR signal intensities typically expected for metastases (slightly hyperintense on non-contrast T1-weighted images and hypointense on T2-weighted images compared to the vitreous body) were seen in only 23.1%. The typical melanoma signal of either moderate or strong hyperintensity on T1-weighted images and hypointensity on T2-weighted images was seen in 69.4% of the proven melanomas. Contrast enhancement was observed in both metastases and melanomas. Morphological differences between metastases and melanomas were detected in tumor size, shape, position, frequency of retinal detachment, and homogeneity of the tumor. Differentiation between intraocular metastases and uveal melanoma is limited by overlap of signal intensities. Some improvement is achieved with morphologic criteria.

Eye imaging with a 3.0-T MRI using a surface coil : a study on volunteers and initial patients with uveal melanoma

MRI of uveal melanoma using 1.5-T technology and surface coils has developed into a standard procedure. The purpose of the study was to evaluate the feasibility of 3.0-T technology in eye imaging. To optimize the MRI sequences for clinical eye imaging with 3.0-T, six healthy volunteers were conducted using a 4.0-cm surface coil. Evaluation criteria were the signal-to-noise-ratio (SNR), contrast-to-noise-ratio (CNR) and image quality. A further six patients with uveal melanoma were examined with 1.5- and 3.0-T under retrobulbar anesthesia. During 3.0-T examinations of volunteers, eye movements caused significant artifacts. On the contrary, excellent imaging quality was reached in examinations of patients under retrobulbar anesthesia at 3.0 T. Subjective assessment showed no significant difference between 1.5 and 3.0 T in patients. Due to the increased SNR, the 3.0-T technique has the potential to improve eye imaging, but the higher susceptibility to motion artifacts limits the clinical use of this technique to patients receiving retrobulbar anesthesia.

Proton therapy of uveal melanomas : Intercomparison of MRI-based and conventional treatment planning

Background and Purpose:Proton therapy for uveal melanoma provides high-conformal dose application to the target volume and, thus, an optimal saving of the organs at risk nearby. Treatment planning is done with the model-based treatment-planning system EYEPLAN. Tumor reconstruction is based only on a fundus composite, which often leads to an overestimation of the clinical target volume (CTV). The purpose was to exploit MRI on trial in a proton therapy-planning system by using the novel image-based treatment-planning system OCTOPUS.Patients and Methods:Ten patients with uveal melanomas received both a high-resolution planning CT and MRI of the eye. MR examinations were made with an eye coil. EYEPLAN requires eye geometry data for modeling, and tantalum marker clips for submillimeter positioning and additional information from ultrasound and 3-D imaging. By contrast, OCTOPUS provides the full integration of 3-D imaging (e. g., CT, MRI). CTVs were delineated in each slice. For all patients, CTVs (EYEPLAN vs. OCTOPUS) were compared intraindividually.Results:OCTOPUS planning led to a mean reduction of the target volume by a factor of 1.7 (T1-weighted [T1w]) and 2.2 (T2w) without compromising safety. The corresponding field size could be scaled down on average by a factor of 1.2 (T1w) and 1.4 (T2w), respectively.Conclusion:Compared with the conventional EYEPLAN, MRI-based treatment planning of ocular tumors with OCTOPUS could be a powerful tool for reducing the CTV and, consequently, the treatment volume and the field size. This might be translated into a better patient compliance during treatment and a decreased late toxicity.Hintergrund und Ziel:Mit der Protonentherapie ist man bei Aderhautmelanomen in der Lage, das Zielvolumen mit hohen Dosen zu belegen und benachbarte Risikoorgane zu schonen. Bei Verwendung des modellbasierten EYEPLAN-Systems führt die Rekonstruktion anhand der Fundusdaten in den meisten Fällen zu einer Überschätzung des klinischen Zielvolumens (CTV). Ziel dieser Studie war es, mit Hilfe des neuen Bestrahlungsplanungssystems OCTOPUS Bestrahlungsplanungen MRT-basiert durchzuführen und mit der konventionellen Planung zu vergleichen.Patienten und Methodik:Zehn Patienten mit Aderhautmelanomen erhielten ein hochauflösendes CT sowie T1- (T1w) und T2-gewichtete (T2w) MRT-Untersuchungen des Auges. Für die Bestrahlungsplanung mit EYEPLAN wurden ein Fundusfoto und Tantalplättchen als Landmarken für die genaue Positionierung des Auges benötigt sowie Informationen aus Ultraschallmessungen und den klinischen 3-D-Bilddatensätzen (CT und MRT) hinzugezogen. OCTOPUS bietet die Möglichkeit, 3-D-Datensätze (CT, MRT) in den Planungsprozess zu integrieren. Das CTV wurde für OCTOPUS und EYEPLAN generiert und für beide Verfahren intraindividuell verglichen.Ergebnisse:Mittels OCTOPUS konnte eine mittlere Reduktion des Zielvolumens um den Faktor 1,7 (T1w) und 2,2 (T2w) erreicht werden, ohne die Therapiesicherheit zu beeinträchtigen. Die Feldgröße konnte im Mittel um den Faktor 1,2 (T1w) bzw. 1,4 (T2w) im Vergleich zu den jeweiligen Werten aus EYEPLAN verkleinert werden.Schlussfolgerung:Verglichen mit dem standardmäßig verwendeten EYEPLAN ist die MRT-basierte Bestrahlungsplanung mit OCTOPUS geeignet, reduzierte CTV, folglich auch reduzierte bestrahlte Volumina und besser an den Tumor angepasste Feldgrößen zu erzeugen. Die resultierende reduzierte Spättoxizität an den kritischen Strukturen gilt es nachzuweisen.

MR anatomy and small lesions of the eye: improved delineation with a special surface coil.

Abstract. To develop an improved investigation protocol for MRI studies of intraocular lesions, imaging with a small surface coil (diameter 6 cm) was compared with a standard surface coil (diameter 11 cm). Both coils were assessed initially on an eye phantom and then by studying 22 patients with uveal melanoma and similar lesions of the eye. The influence of bandwidth and field or view (FOV) were systematically studied and evaluated quantitatively. A smaller bandwidth improved image quality independent of surface coil size. The subsequent secondary increase in chemical shift artefact was acceptable. Smaller FOVs (60–80 mm) necessitated the use of a smaller surface coil. A smaller bandwidth also proved to be advantageous with the use of the smaller surface coil. In conclusion, a smaller-diameter surface coil improves MR imaging of ocular lesions. Pulse sequences with a small bandwidth maintain an acceptable signal-to-noise ratio when the FOV is reduced.